Static longitudinal stability of tailless airplane is evaluated theoretically with two methods. One is quasi (or modified)-strip method and the other is a lifting surface theory—DLM. Computation is made on the basis of available data of Northrop XB-35. The both methods agree each other only qualitatively; of course results of DLM should be much more reliable. Allowable limit of longitudinal CG position may be almost comparable with that of conventional airplanes. The airplane efficiency factor, e concerning with induced drag, is computed which is also satisfactory at least for cruising configuration.